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United States Patent |
5,268,109
|
Boyd
|
December 7, 1993
|
Method of removing hydrocarbon contaminants from air and water with
organophilic, quaternary ammonium ion-exchanged smectite clay
Abstract
A method of removing hydrocarbon contaminants from air and a method of
removing nonionic organic contaminants, particularly petroleum-derived
aromatic contaminants that have a limited capacity to ionize in aqueous
solution at substantially neutral pH, from water, by contacting the
contaminants in the air or water with an organophilic clay that has been
prepared by ion-exchange of an ion-exchangeable clay with a tetra short
chain alkyl C.sub.1 -C.sub.4), quaternary ammonium ion for use in removing
air-laden contaminants; or a di- or tri- short chain alkyl (C.sub.1
-C.sub.4), with one or two mono- substituted or unsubstituted cycloalkyl
moieties, or one or two mono-substituted or unsubstituted aryl or one or
two alkaryl moiety quaternary ammonium ion for removing air and
water-laden contaminants. The method is particularly adapted for removal
of aromatic petroleum-based contaminants from water, such as benzene,
toluene, xylene (o, m and p) ethylbenzene and naphthalene, and other
water-contained petroleum constituents or derivatives that have a pKa in
aqueous solution of at least about 10.
Inventors:
|
Boyd; Stephen A. (1825 Linden, East Lansing, MI 48823)
|
Appl. No.:
|
032523 |
Filed:
|
March 15, 1993 |
Current U.S. Class: |
210/691; 95/141; 95/142; 210/147; 210/909 |
Intern'l Class: |
B01D 053/02; C02F 001/28 |
Field of Search: |
55/74
210/691,679,909
|
References Cited
U.S. Patent Documents
4386010 | May., 1983 | Hildebrandt | 252/428.
|
4470912 | Sep., 1984 | Beall | 210/691.
|
4861491 | Aug., 1989 | Svensson | 210/691.
|
Foreign Patent Documents |
0181508A3 | May., 1986 | EP.
| |
0398410A1 | Nov., 1990 | EP.
| |
1235460 | May., 1960 | FR.
| |
Primary Examiner: Cintins; Ivars
Attorney, Agent or Firm: Marshall, O'Toole, Gerstein, Murray & Borun
Parent Case Text
This is a continuation of U.S. application Ser. No. 07/575,963, filed Aug.
31, 1990, now abandoned.
Claims
What is claimed and desired to be secured by Letters Patent of the United
States is:
1. A method of adsorbing an aromatic organic compound having a pKa of at
least 10, from air or water comprising contacting the organic compound
with a quaternary ammonium ion-exchanged colloidal clay including a
quaternary ammonium ion-exchanged cation of the formula:
##STR12##
wherein R is a moiety selected from the group consisting of substituted or
unsubstituted cycloalkyl having 3 to about 7 carbon atoms; substituted or
unsubstituted aryl and wherein R' is C.sub.1 -C.sub.4 or a substituted or
unsubstituted cycloalkyl moiety having 3 to about 7 carbon atoms; or a
substituted or unsubstituted aryl moiety or a substituted or unsubstituted
alkaryl moiety, wherein the alkyl of the alkaryl moiety has from 1 to
about 4 carbon atoms.
2. The method of claim 1 wherein R is a cycloalkyl moiety having 3 to about
7 carbon atoms.
3. The method of claim 1 wherein R is benzyl or phenyl.
4. The method of claim 1 wherein the organic compound is selected from the
group consisting of a petroleum component, a petroleum derivative, and
combinations thereof.
5. The method of claim 1 wherein the organic compound is selected from the
group consisting of benzene, toluene o-xylene, m-xylene, p-xylene,
ethylbenzene, butylbenzene, naphthalene, polychlorinated biphenyls,
dioxin, and mixtures thereof.
6. The method of claim 5 wherein R is benzyl or phenyl.
7. The method of claim 6 wherein the clay is a smectite clay.
8. The method of claim 7 wherein R is a cycloalkyl moiety having three to
about seven carbon atoms.
9. The method of claim 5 wherein R is an aryl moiety having 3 to about 7
carbon atoms.
10. The method of claim 1 wherein R is a substituted or unsubstituted aryl
moiety selected from the group consisting of phenyl, napthenyl, trienyl,
pyridyl, pyrrolyl, furyl, pyrazolyl, pyradazinyl, pyrimidyl, quinolyl,
isoquinolyl, benzyl, and acridinyl.
11. The method of claim 1 wherein one or both of R and R' are a substituted
alkaryl moiety, wherein the alkyl or the alkaryl moiety has from 1 to
about 4 carbon atoms wherein the alkaryl moiety is substituted with a
functionality selected from the group consisting of a hydroxy; alkoxy
(--OR); alkyl (--R); halo (--X); amino (--NH.sub.2), --NHR, --NR.sub.2,
--NR.sub.3); nitro (--NO.sub.2); cyano (--CN); alkyl sulfonyl (--SO.sub.2
R); mercapto (--SH); alkylthio (--SR); carbonyl (--COY); and mixtures
thereof; wherein R is an alkyl group having 1 to about 4 carbon atoms; X
is a halogen atom selected from chloro, bromo and fluoro; and Y is
selected from hydrogen, hydroxy, alkoxy, haloamino and alkyl having 1 to
about 4 carbon atoms.
12. The method of claim 1 wherein the cation has the formula:
##STR13##
13. The method of claim 1 wherein the cation has the formula:
##STR14##
14. The method of claim 1 wherein the cation has the formula:
##STR15##
15. The method of claim 1 wherein R is an aryl moiety having 3 to about 7
carbon atoms.
16. A method of adsorbing benzene from water comprising contacting the
benzene-containing water with a trimethylphenylammonium ion-exchanged
smectite clay.
17. A method of adsorbing an aromatic organic compound from water, wherein
the organic compound is selected from the group consisting of benzene,
toluene, ethylbenzene, xylene, butylbenzene, naphthalene, and mixtures
thereof, comprising contacting the organic compound-containing water with
a trimethylphenylammonium ion-exchanged smectite clay.
18. A method of adsorbing an aromatic organic compound from water, wherein
the organic compound is selected from the group consisting of benzene,
toluene, ethylbenzene, xylene, butylbenzene, naphthalene, and mixtures
thereof, comprising contacting the organic compound-containing water with
an ion-exchanged clay selected from the group consisting of a
trimethylphenylammonium ion-exchanged smectite clay, a tetramethylammonium
ion-exchanged smectite clay, and mixtures thereof.
Description
FIELD OF THE INVENTION
The present invention is directed to a chemically modified clay, such as a
smectite clay, to render the clay organophilic and to a method of using
the chemically modified clay to adsorb aliphatic and aromatic hydrocarbon
contaminants from gases, particularly air; and for adsorption of
hydrocarbon contaminants from aqueous solutions.
More particularly, the present invention is directed to a
cation-exchangeable clay that has been chemically modified to attach a
quaternary ammonium ion that includes a) four short chain alkyl moieties
(C.sub.1 -C.sub.4) bonded to the quaternary nitrogen atom, e.g.
tetramethyl; b) two or three short chain alkyl moieties (C.sub.1 -C.sub.4)
and one or two substituted or unsubstituted cycloalkyl; substituted or
unsubstituted aryl or alkaryl moiety, e.g. benzyl or phenyl; c) alkylated
diazobicyclo ions, such as 1,4-diazobicyclo [2.2.2.] octane (DABCO); or
alkyl diammonium cations, such as decyltrimethyldiammonium (DTMA) ions, to
provide a modified clay, such as a smectite clay, capable of removing,
from water, nonionic organic compounds, (NOCs) such as aliphatic
hydrocarbons from air, aliphatic hydrocarbons from water and aromatic
hydrocarbons from water that have a pKa in aqueous solution of at least
10. The chemically modified clays function by adsorbing the organic
contaminants from gases, e.g. air, or by adsorbing the contaminants from
water onto the surface of the clay, as opposed to the known mechanism of
prior art organophilic clays in acting as partition phases between the
smectite clay interlamellar surfaces for sorption of water-soluble
contaminants.
BACKGROUND OF THE INVENTION AND PRIOR ART
Bentonite (smectite) clays are used widely in the construction of liners
for hazardous waste landfills, slurry walls, industrial waste treatment
lagoons, sewage lagoons, and tank farms. The utility of clays as
waterproofing barriers or liners is derived from their ability to
disaggregate upon hydration and form a dispersed phase of very small
particles. These small clay particles effectively fill the void spaces
between larger soil particles resulting in greatly reduced hydraulic
conductivity. Thus, the primary function of clay liners, as well as
synthetic geo-membraines, is to impede the movement of water.
Smectite clays contain a net negative charge due to isomorphous
substitution in the aluminosilicate layers. In nature, this charge is
neutralized by cations such as Na.sup.+ or Ca.sup.2+ on the clay
interlayers and external surfaces. Hydration of these cations in the
presence of water initiates a separation of the clay layers causing a
swelling of the clay. In smectites exchanged with monovalent cations
having high hydration energies, e.g., Na.sup.+ or Li.sup.+, the individual
clay platelets may become completely separated in the presence of water.
However, the maximum distance between individual clay layers of divalent
cation-exchanged smectites, e.g., Ca.sup.2+, Mg.sup.2+, is about 19
Angstroms. Thus, in the construction of clay liners, Na-smectites are more
effective in reducing hydraulic conductivity because they form small
highly-dispersed particles in water.
The hydration of naturally occurring metal exchange ions on clays also
imparts a hydrophilic nature to the clay surfaces. As a result, natural
clays are ineffective in removing nonionic organic contaminants (NOCs)
from water. However, by simple ion-exchange reactions, the naturally
occurring inorganic exchange ions of clays can be replaced by a variety of
organic cations and this may change the clay surface from hydrophilic to
organophilic. These ion-exchange reactions can be used to form stable
organo-clay complexes with high affinities for organic contaminants. Such
organo-clays can be used in conjunction with conventional clays to
increase the containment capabilities of clay barriers by immobilizing
organic contaminants present in leachate. The sorptive properties of soils
for NOCs also can be greatly enhanced by organic cation exchange of soil
clays. Other possible environmental applications of organo-clays are in
the stabilization/solidification of industrial wastes and in water
purification.
It is possible to modify the surface properties of clays greatly by
replacing natural inorganic exchange cations by larger alkylammonium ions.
These ions act as `pillars` which hold the aluminosilicate sheets
permanently apart. In the modified form, the clay surface may become
organophilic and interact strongly with organic vapours and with organic
compounds dissolved in water. These organo-clays are now able to sorb
alkanes and aliphatic alcohols to remove organic contaminants from water,
and to serve as chromatographic stationary phases.
Until recently, the literature on the sorptive behaviour of organo-clays
has been concerned almost exclusively with the organic vapour uptake by
dry modified-clay samples. Mortland et al, 1986, Clays and Clay Minerals
34, 581, have studied the uptake of phenol and chlorophenols from aqueous
solution by smectites whose cations were exchanged by quaternary ammonium
ions of the form [(CH.sub.3).sub.3 -NR].sup.+ where R is an alkyl group.
In general, it was found that where R was a large non-polar alkyl group
(e.g., R.dbd.C.sub.16 H.sub.33) the modified clay samples exhibited
greatly improved sorption capacities in comparison with unmodified clays
or modified clays in which the exchanged organic ions were small in size.
It was also found that smectite exchanged with a small tetramethylammonium
ion (herein referred to as TMA-smectite) exhibited much higher affinity
for benzene from water than for less water-soluble and large sized
1,2,4-trichlorobenzene, McBride, et al., 1977, in Fate of Pollutants in
the Air and Water Environment, Part 1, Vol. 8, pp. 145-154. The extent of
benzene uptake by the TMA-smectite was also much greater than by clays
exchanged with tetraethylammonium ion (TEA), or with
hexadecyltrimethylammonium ion (HDTMA), in the sequence of TMA-smectite
>HDTMA-smectite >TEA-smectite. These studies indicated that the exchanged
organic ions affected the sorptive behaviour of clay in some manner that
appeared to be related to the size and molecular arrangement of the
exchanged ion in the clay.
The sorption characteristics of benzene and trichloroethylene (TCE) on
HDTMA-smectite were studied from both aqueous solution and the vapour
phase, Boyd et al., Soil Science Society of America Journal, 1988, 52,
652. It was found that the dry HDTMA-smectite behaved as a dual sorbent,
in much the same fashion as dry soil, in which the bare mineral surfaces
function as a solid absorbent and the exchanged HDTMA organic ions
function as a partition medium. In aqueous solution, adsorption of
non-ionic organic compounds by free mineral surfaces is minimized by the
strong competitive adsorption of water, and the uptake of organic solutes
by the modified clay is effected mainly by solute partitioning in the
organic medium that is formed by conglomeration of large C.sub.16 alkyl
groups associated with HDTMA. The presumed partition effect with the
HDTMA-smectite is supported by the linear sorption isotherm, lack of a
competitive effect between organic solutes, and the dependence of the
sorption capacity on the amount of HDTMA in clay. The uptake of organic
vapours by dry HDTMA-smectite was greater than by water-saturated
HDTMA-smectite because of concurrent adsorption on mineral surfaces, and
consequently, vapour uptake isotherms were not linear. The improved
sorption of benzene and TCE from water by HDTMA-smectite over that by pure
clays was attributed to partition into the highly non-polar hydrocarbon
medium.
Improvement of the sorption capacity of soils with low organic matter
contents was similarly achieved by cation exchange reactions with HDTMA
ions. This study also demonstrated that HDTMA-derived organic matter added
to soil was 10-30 times more effective on a unit weight basis than natural
soil organic matter for removing organic contaminants from water. A more
detailed analysis of this phenomena appears at Environ. Science Technol.,
1989, Vol 23 pg. 1365-1370, hereby incorporated by reference.
The organo clays (organo-smectites, and illites and vermiculites) that
include a large alkyl quaternary ammonium hydrocarbon radical, for
example, hexadecyltrimethylammonium (HDTMA) appear to form partition
phases, fixed on the clay surfaces or interlayers, that are derived from
the large alkyl hydrocarbon moieties bonded to the quaternary ammonium
nitrogen atom. These partition phases are compositionally and functionally
similar to bulk phase hydrocarbon solvents such as hexane or octonol. The
sorption of organic solutes from water by these organo-clays show
characteristics of solute partitioning including linear isotherms, inverse
dependence of the sorption coefficient on the water solubility of the
solute, and correspondence between the organic matter normalized sorption
coefficients (K.sub.om) and the octanol-water partition coefficients. The
effectiveness of HDTMA-clays can be increased by using clays with high
cation-exchange capacities and high surface charge densities.
It has been discovered that the characteristics of NOC sorption from water
by smectite clays exchanged with tetramethylammonium ions were completely
different from the partition behavior of clays exchanged with large
organic cations such as HDTMA. Due to their small size, TMA ions exist as
discrete entites on the smectite layers, and therefore do not form
partition phases. Rather, TMA-smectite behaves as a surface adsorbent for
aliphatic and aromatic hydrocarbons, such as benzene and substituted
benzenes and this is manifested in nonlinear sorption isotherms and strong
competitive effects in binary solute mixtures. J. F. Lee. M. M. Mortland,
C. T. Chiou, S. A. Boyd. "Shape selective adsorption of aromatic molecules
from water by tetramethylammoniumsmectite." J. Chem. Soc., Faraday Trans.
1, 85, 2953(1989); and J. F. Lee, M. M. Mortland, C. T. Chiou, D. E. Kile,
S. A. Boyd. "Adsorption of benzene, toluene, and xylene by two
tetramethylammonium-smectites having different charge densities." Clays
and Clay Minerals. 38, 113 (1990), both hereby incorporated by reference.
Tetramethylammonium smectite was shown to be an especially effective
adsorbent for removing benzene from water, and for removing benzene vapors
from air, exhibiting greater uptake of benzene than HDTMA-smectite.
However, TMA-smectite also displayed strong shape selectivity resulting in
progressively lower uptake of larger aromatic molecules such as toluene,
xylene and ethylbenzene from water, but did not show selectivity for
removing organic vapors from air.
Tetramethylammonium-smectite has been studied for removal of organic
contaminants from water and for chromatographic use in determining the
presence and/or concentration of organic contaminants in air, but has not
been disclosed as practically useful for removing hydrocarbon contaminants
from gases such as air.
Trimethylphenylammonium-smectite has been studied for removing phenol and
chlorophenols from water with very limited success (see M. M. Mortland et
al., Clays and Clay Minerals. 34, 581 (1986). It is theorized that the
ineffectiveness of trimethylphenylammonium-smectite for removal of
phenol-based contaminants was due to the relatively high ionization
potential of the phenol OH moiety leaving a negatively charged phenolate
molecule that cannot be absorbed or adsorbed sufficiently by the
negatively charged clay molecules.
Unexpectedly, it has been found that ion-exchangable clays such as the
montmorillonites or smectites, particularly the bentonites that have
sodium, potassium, lithium magnesium or calcium as their predominant
exchangable cations; as well as hectorite; saponite; nontronite;
attapulgite; illite; zeolites; vermiculite, and the like, that are
ion-exchanged with a) a tetra-short chain alkyl quaternary ammonium
compound, e.g. tetramethyl; ion-exchanged with b) a quaternary ammonium
compound having two or three short chain alkyl moieties, and one or two
mono- substituted or unsubstituted cycloalkyl, or a mono- substituted or
unsubstituted aryl or alkaryl moieties, e.g. benzyl or phenyl; c)
alkylated diazobicyco ions, such as 1,4-diazobicyclo [2.2.2.] (DABCO); or
alkyldiammonium cations, such as decyltrimethydiammonium (DTMA) ions,
effectively adsorb or otherwise remove aliphatic and aromatic hydrocarbon
contaminants from gases, e.g. air, and from water, provided that when the
contaminants are removed from water, the contaminants have a pKa in
aqueous solution (negative log of the acid dissociation constant) of at
least about 10.
SUMMARY OF THE INVENTION
In brief, the present invention is directed to a new and improved method of
removing hydrocarbon contaminants from air and a method of removing
nonionic organic contaminants, particularly petroleum-derived aromatic
contaminants that have a limited capacity to ionize in aqueous solution at
substantially neutral pH, from water, by contacting the contaminants in
the air or water with an organophilic clay that has been prepared by
ion-exchange of an ion-exchangeable clay with a tetra short chain alkyl
(C.sub.1 -C.sub.4) quaternary ammonium ion for use in removing air-laden
contaminants; or a di- or tri- short chain alkyl (C.sub.1 -C.sub.4), with
one or two mono-substituted or unsubstituted cycloalkyl, or one or two
mono- substituted or unsubstituted aryl or one or two alkaryl moiety
quaternary ammonium ion for removing air and water-laden contaminants. The
method of the present invention is particularly adapted for removal of
aromatic petroleum-based contaminants from water, such as benzene,
toluene, xylene (o, m and p) ethylbenzene and naphthalene, and other
water-contained petroleum constituents or derivatives that have a pKa in
aqueous solution of at least about 10.
Accordingly, one aspect of the present invention is to provide a new and
improved method of removing an nonionic organic contaminant from water by
contacting the contaminant with an ion-exchanged smectite clay, wherein
the nonionic organic contaminant is aliphatic or the contaminant is
aromatic and has a pKa in aqueous solution of at least 10, wherein the
ion-exchanged smectite clay includes a quaternary ammonium ion of the
formula:
##STR1##
wherein R is a substituted or unsubstituted cycloalkyl moiety or a
substituted or unsubstituted aryl or alkaryl moiety, and wherein R' is
(C.sub.1 -C.sub.4) or a substituted or unsubstituted cycloalkyl moiety or
a substituted or unsubstituted aryl or alkaryl moiety.
Another aspect of the present invention is to provide a new and improved
method of removing non-ionic organic contaminants from air by contacting
the contaminants with an ion-exchanged smectite clay that includes a
quaternary ammonium ion of the formula:
##STR2##
In accordance with another embodiment of the present invention, the
quaternary ammonium ion exchanged with the clay cations can be a
di-quaternary ammonium ion, particularly di-quaternary ammonium ions
selected from the group consisting of alkylated diazobicyclo di-quaternary
ammonium ions and C.sub.1 -C.sub.20 trialkyl (C.sub.1 -C.sub.4)
di-quaternary ammonium ions.
Suitable alkylated (C.sub.1 -C.sub.4) diazobicyclo ions useful for
adsorbing organic contaminants from gases, such as air, and from water
include the diazobicyclo compounds that have C.sub.8 -C.sub.14 membered
rings wherein two of the carbon atoms of the ring structure have been
substituted with nitrogen atoms. A particularly suitable alkylated
(C.sub.1 -C.sub.4) diazobicyclo ion is 1,4-diazobicyclo [2.2.2.] octane,
wherein the alkyl moiety is CH.sub.3 :
##STR3##
Other suitable alkylated diazobicyclo ions include
1,4--Diazobicyclo [3.2.2] nonane; 1,4--Diazobicyclo [3.3.2] decane;
1,5--Diazobicyclo [3.3.3] undecane; 1,4--Diazobicyclo [4.2.2] decane;
1,4--Diazobicyclo [4.3.2] undecane; 1,5--Diazobicyclo [4.3.3] dodecane;
1,5--Diazobicyclo [4.4.3] tridecane; 1,6--Diazobicyclo [4.4.4]
tetradecane; and 1,4--Diazobicyclo [4.4.2]dodecane.
Another class of diammonium compounds that are useful for adsorbing
nonionic organic hydrocarbons from gases, such as air, and from water
include the alkyldiammonium ions having a general formula:
##STR4##
such as the decyltrimethyldiammonium (DTMDA) ion:
##STR5##
These and other aspects and advantages of the present invention will become
more apparent from the following detailed description of the preferred
embodiments, taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph showing the adsorption of trimethylphenylammonium on
Mg-smectite (SAC);
FIG. 2 is a graph showing the adsorption of aromatic hydrocarbons on
trimethylphenylammonium (TMPA)- and tetramethylammonium (TMA)-smectite
(SAC);
FIG. 3 is a graph showing the adsorption of benzene and toluene on low
charge (SAC)-and high-charge (SWa)-trimethylphenylammonium smectites; and
FIG. 4 is a graph showing absorption of benzene by smectite clay (SAC)
exchanged with tetramethylammonium (TMA), dimethyl- 1,4-diazobicyclo
[2.2.2] octane (DM-CABCO), 1,4-diazobicyclo [2.2.2] octane (DABCO), and
trimethyl-phenylammonium (TMPA).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The clays that can be ion-exchanged with the quaternary ammonium ions
disclosed herein can be any clay capable of sufficient low-exchange with
the quaternary ammonium ions described to render the clays organophilic.
Preferably, the water-swellable colloidal clay that can be ion-exchanged
with the quaternary ammonium compounds described herein include any
water-swellable clay which will hydrate in the presence of water, i.e.,
will swell in the presence of water. In accordance with one important
embodiment of the present invention, the clay is bentonite. A preferred
bentonite is sodium bentonite which is basically a hydratable
montmorillonite clay of the type generally found in the Black Hills region
of South Dakota and Wyoming. This clay has sodium as a predominant
exchange ion. However, the bentonite utilized in accordance with this
embodiment of the present invention may also contain other cations such as
lithium, potassium, calcium, ammonium, magnesium and iron.
There are cases wherein a montmorillonite predominant in calcium ions can
be converted to a high swelling sodium variety through a well known
process called "peptizing". The clay utilized in this invention may be one
or more peptized bentonites. The clay may also be any member of the
dioctahedral or trioctahedral smectite group or mixtures thereof. Examples
are Beidellite, Nontronite, Hectorite and Saponite. Attapulgite, illite
and vermiculite also are useful in accordance with the present invention.
To achieve the full advantage of the present invention, the colloidal
clay, e.g., bentonite, generally is finely divided as known for use in
water barrier panels and the like, i.e. 150 to 350 mesh.
The cation-exchange capacities of these clays are well known and sufficient
quaternary ammonium compound is dissolved in aqueous solution in contact
with the ground or otherwise finely divided colloidal clay in aqueous
suspension to achieve sufficient quaternary ammonium ion cation exchange
to render the clay organophilic. Sufficient time is allowed for complete
cation exchange, e.g. 30 minutes to 24 hours, with two to four hours being
a sufficient time for complete cation exchange for most clays. A
stoichiometric excess of quaternary ammonium compound of two to five times
the cation exchange capacity of the clay is preferred to assure quaternary
ammonium ion-exchange as complete as possible with the colloidal clay.
After cation exchange, the excess quaternary ammonium cations, quaternary
ammonium anions, any precipitated salts, and cations removed from the clay
in the cation exchange are removed by filtration, dialysis or the like,
and the clay is washed in water, e.g. distilled water. For storage
purposes, the resulting organophilic ion-exchanged clay can be frozen
and/or freeze dried to maintain the organic ion-exchange capacity for long
periods of time.
For purposes of removing organic contaminants from gases, such as air, it
has been found that excellent results are achieved with a quaternary
ammonium compound of the formula:
##STR6##
for example tetramethylammonium chloride or bromide, tetraethylammonium
chloride or bromide, tetrapropylammonium chloride or bromide,
tetrabutylammonium chloride or bromide, trimethylmonoethylammonium
chloride or bromide, or any other combination of C.sub.1 -C.sub.4 radicals
capable of synthesis. The particular anion associated with the quaternary
ammonium cation is of no significant consequence in the ion-exchange
reaction with the clay.
For removal of gas-laden or water-laden organic aliphatic contaminants, and
aromatic contaminants having a pKa of at least 10, the quaternary ammonium
compound that is ion exchanged with the colloidal clay should have a
formula:
##STR7##
Wherein R is a substituted or unsubstituted cycloalkyl moiety; a
substituted or unsubstituted aryl moiety; or a substituted or
unsubstituted alkaryl moiety, and wherein R' is C.sub.1 -C.sub.4 or a
substituted or unsubstituted cycloalkyl moiety or a substituted or
unsubstituted aryl or alkaryl moiety. With respect to each of these
moieties R, the cycloalkyl moieties can have from three to about seven
carbon atoms. The aryl moiety of the substituted and unsubstituted aryl
and/or alkaryl moieties can be, for example, phenyl, napthenyl, trienyl,
pyridyl, pyrolyl, pyridyl, furyl, pyrazolyl, pyridazinyl, pyrimidyl,
quinolyl, isoquinolyl, acridinyl and similar five-numbered and
six-numbered carbocyclic and heterocyclic aromatic compounds; and wherein
the alkaryl moiety is benzyl, 2-phenylethyl and similar aryl-substituted
alkyl groups including from one to about four carbon atoms; and wherein
the aryl or alkaryl moiety is substituted within a functionality such as,
for example, hydroxy (--OH); alkoxy (--OR); alkyl (--R); halo (--X), amino
(--NH.sub.2, --NHR, --NR.sub.2); nitro (--NO.sub.2); cyano (--CN); alkyl
sulfonyl (--SO.sub.2 R); mercapto (--CH); alkylthio (--SR); carbonyl
functionalities having the formula --CO--Y, wherein Y is hydrogen,
hydroxy, alkoxy, halo amino, or alkyl; and combinations thereof, wherein R
is an alkyl group including from one carbon atom to about 20 carbon atoms
and X is chloro, bromo or fluoro.
In accordance with another embodiment of the present invention, the
quaternary ammonium ion exchanged with the colloidal clay cations can be a
di-quaternary ammonium, particularly di-quaternary ammonium compounds
selected from the group consisting of alkylated diazobicyclo di-quaternary
ammonium ions and C.sub.1 -C.sub.20 trialkyl diammonium quaternary
ammonium ions.
Suitable alkylated (C.sub.1 -C.sub.4) methylated diazobicydo ions useful
for adsorbing organic contaminants from gases, such as air, and from water
include the diazobicyclo compounds that have C.sub.8 -C membered rings
wherein two of the carbon atoms of the ring structure have been
substituted with nitrogen atoms. A particularly suitable alkylated
(C.sub.1 -C.sub.4) diazobicyclo ion is 1,4-diazobicyclo [2.2.2.] octane,
wherein the alkyl moiety is CH.sub.3 :
##STR8##
Other suitable alkylated diazobicyclo ions include:
1,4--Diazobicyclo[3.2.2] nonane; include: 1,4--Diazobicyclo [3.2.2]
nonane; 1,4 Diazobicyclo [3.3.2] decane; 1,5--Diazobicyclo [3.3.3]
undecane; 1,4--Diazobicyclo [4.3.2] decane; [1,4--Diazobicyclo [4.3.2]
undecane; 1,5--Diazobicyclo 4.3.3] dedecane; 1,5--Diazobicyclo [4.4.3]
tridecane; 1,6--Diazobicyclo [4.4.4] tetradecane; and 1,4--Diazobicyclo
[4.4.2] dedecane.
Another class of diammonium compounds that is useful for adsorbing nonionic
organic hydrocarbons from gases, such as air, and from water include the
alkyldiammonium ions having a general formula:
##STR9##
such as the decyltrimethyldiammonium (DTMDA) ion:
##STR10##
These ion-exchanged clays are particularly effective for removing nonionic
organic contaminants, halogenated hydrocarbons, and derivatives of
petroleum-derived organic contaminants from gases, e.g. air, and water,
such as benzene, toluene, ethylbenzene, o, m, and p-xylene, butylbenzene,
napthalene, carbontetrachloride, chloroform, mono-chloroethane,
di-chloroethane, tri-chloroethane, tetrachloroethane, mono-, di-, tri- and
tetrachloroethenes, polychlorinated biphenyls, dioxin, and other common
oil-spill problem contaminants, provided that the contaminants have a pKa
of at least about 10 in water.
A Wyoming bentonite (SAC) and a South Carolina vermiculite (VSC) sample
were obtained from the American Colloid and Zonolite companies,
respectively. The bentonite is primarily composed of low-charge smectite
The vermiculite contains biotite and hydrobiotite. Ferruginous smectite
(nontronite) (SWa) was obtained from the Source Clay Repository of The
Clay Minerals Society. The <2 .mu.m clay fractions were obtained by wet
sedimentation and were subsequently Na-saturated, frozen, and
freeze-dried. The mineralogy and properties of the clays used in this
study are summarized in TABLES 1 and 2.
TABLE 1
______________________________________
Mineralogy and Source of Samples
Sample
Desig-
nation Mineralogy Origin Source
______________________________________
SAC low-charge Wyoming American
smectite, <2 .mu.m
bentonite Colloid Co.
SWa high charge <2 .mu.m
Grant Co., Clay Minerals
smectite Washington Society
(nontronite) Repository
VSC vermiculite, South Carolina
Zonolite Co.
hydrobiotite
______________________________________
TABLE 2
______________________________________
Properties of Clay Minerals and Derived
Trimethylphenylammonium (TMPA)-
and Tetramethylammonium (TMA)-Clays
Cation Exchange
Charge Organic
Capacity (mol.sup.- /
Carbon .sup.d 001
Sample (cmol.sup.- /kg)
unit cell)
(%) (.ANG.)
______________________________________
SAC 90 0.64 -- --
SAC-TMPA 9.15 14.5
SAC-TMA 3.66 14.0
SWa 107 0.96 -- --
SWa-TMPA 9.66 15.2
SWa-TMA 4.01 14.2
VSC 110 1.32 -- --
VSC-TMPA 5.02 15.1
______________________________________
Tetramethylammonium (TMA) and Trimethyphenylammonium (TMPA) organo-clays
were prepared by adding quantities of the respective chloride salts equal
to five times the cation exchange capacity of the clay. The TMA and TMPA
chlorides were dissolved in distilled water and added to clay suspensions
which were agitated with a magnetic stirrer. After mixing for 4 hours, the
TMA and TMPA clay suspensions were sealed in dialysis tubing and dialyzed
in distilled water until free of salts. The resulting TMA and TMPA clay
suspensions were later quick-frozen and freeze-dried. Organic carbon
analyses were then performed on the organo-clays.
X-Ray Diffraction Analysis
Samples (30 mg) of the TMA- and TMPA-clays were washed with 5 ml of 95%
ethanol, ultrasonically dispersed in 2 ml of 95% ethanol, and dried as
oriented aggregates on glass slides. Basal x-ray diffraction spacings
(TABLE 2) then were recorded using Cuk radiation and a Philips APD 3720
automated x-ray diffractometer consisting of an APD 3521 gonimeter fitted
with a theta-compensating slit, a 0.2-mm receiving slit, and a
diffracted-beam graphite monochromator.
Adsorption Isotherms
The ultraviolet absorbance of TMPA solutions was used to measure TMPA
adsorption to clays. A batch adsorption isotherm of TMPA on Mg-saturated
smectitie (SAC) was obtained using 100 mg samples of clay in 25 ml Corex
centrifuge tubes. Aqueous solutions of TMPA chloride equal to about 0.25,
0.50, 0.75, 1.0, 1.25, 1.5, 3.0, and 6.0 times the cation exchange
capacity of the clay were added and the total volume was brought to 20 ml
with distilled water. After shaking for 8-12 hours, the tubes were
centrifuged and the equililbrium solutions were collected. The absorbances
of the equilibrium solutions were measured at 230 nm and converted into
centimoles (cmoles) of TMPA/liter from a standard plot of TMPA
concentration versus absorbance. Differences between TMPA concentrations
in the initial and equilibrium solutions were used to calculate the
quantity adsorbed in cmoles TMPA/kg of clay.
Batch sorption isotherms of benzene, toluene, ethylbenzene, p-xylene,
butylbenzene and naphthalene on the TMA- and TMPA-clays were made by
weighing 0.05 to 0.20 g samples into 25 ml Corex centrifuge tubes that
contained 25 ml of distilled water. Hamilton microliter syringes were used
to deliver a range of concentrations of each compound up to 70% of the
water solubility. Benzene was added directly as the neat liquid, whereas
toluene, ethylbenzene, p-xylene, butylbenzene and naphthalene were
delivered as methanol solutions. To reduce vaporization losses, aluminum
foil liners were placed on the tubes and the teflon-lined caps were
promptly sealed. Blank samples containing 25 ml of distilled water and the
added organic compounds also were prepared to estimate vaporization losses
and adsorption to the glass. Samples were placed on a reciprocating shaker
and agitated for 12-18 hours under ambient conditions. After
centrifugation, a 1 to 5 ml aliquot of the supernatant was extracted with
10 ml of CS.sub.2 in a glass vial. A portion of the CS.sub.2 extract
containing the extracted compound then was analyzed using gas
chromatography.
Isotherms were constructed by plotting the amounts sorbed versus the
concentrations remaining in solution (C.sub.e). The amount sorbed was
calculated from differences between the quantity of organic compound added
and that remaining in the equilibrium solutions. Typical blank recoveries
ranged from 85-95%; the data were not adjusted for these recoveries.
Concentrations of the organic compounds in the CS.sub.2 extracts were
measured with a Hewlett Packard 5890A gas chromatograph using a flame
ionization detector. A packed column with 5% SP-1200/1.75% Bentonite 34
coated on a 100-120 mesh Supelcoport support with N.sub.2 as the carrier
gas was used for all separations. Peak areas were determined with a
Hewlett Packard 3392A integrator and a Hewlett Packard 7673A automatic
sample changer was used to automate runs.
An adsorption isotherm representing the ion-exchange of TMPA to a
Mg-saturated smectite (SAC) is shown in FIG. 1. The steep initial rise of
this isotherm shows that Mg.sup.2+ is nearly stoichiometrically displaced
by TMPA until about 90 percent of the cation exchange sites are occupied
by TMPA. Addition of TMPA in excess of the cation exchange capacity
assures complete saturation of the cation exchange sites. The ion-exchange
reaction between TMPA and Na-smectite should be even more favorable than
with Mg-smectite due to the greater exchangeability of monovalent cations.
Organic carbon contents and basal spacings of the TMPA- and TMA- smectites
are presented in Table 2. The organic carbon contents of the
organo-smectites indicate that the cation exchange sites are completely
occupied by the organic cations. However, the organic carbon content of
the TMPA-exchanged vermiculite indicates that TMPA occupies only about 60
percent of the exchange sites. This likely results from the limited
swelling of Na-vermiculite in water (14.5 Angstroms), and the larger
particle size of vermiculite, which imposes a diffusional limit on the
exchange reaction.
The x-ray diffraction basal spacings (d.sub.001) of the TMPA- and
TMA-smectites were between 14 and 15.2 Angstroms. The basal spacings of
the TMPA-smectites were slightly larger (0.5 to 1.0 Angstroms) than those
of the TMA-smectite, consistent with the larger size of TMPA as compared
to TMA ions. These basal spacings, which include the 2:1 aluminosilicate
sheet (9.4 Angstroms), indicate an interlayer separation (.DELTA.) of
about 4.6 to 4.8 Angstroms for TMA-smectite, and 5.1 to 5.8 Angstroms for
TMPA-smectite. This agrees well with the height of the TMA ion which is
4.9 Angstroms, and suggests some keying of the hydrogen atoms into the
aluminosilicate sheets. These data indicate that the triangular bases of
TMA and TMPA ions are parallel to the clay sheets, and presumably these
bases adhere alternatively to the upper and lower clay layers.
In contrast to TMA-and TMPA-smectites, HDTMA-smectites give much larger
basal spacings of between 18 and 23 Angstroms, depending on the layer
charge of the mineral. These spacings for HDTMA-smectites correspond to
the formation of bilayers and paraffin complexes in which HDTMA ions are
in direct contact with each other, leading to the formation of partition
phases derived from the C.sub.16 hydrocarbon groups.
Isotherms representing the adsorption of benzene, toluene, ethylbenzene,
p-xylene, butylbenzene and naphthalene by TMA- and TMPA-smectite (SAC) are
shown in FIG. 2. Benzene sorption produces a curvlinear Langmuir-type
isotherm on TMA-smectite. A similar isotherm is observed for benzene
sorption on TMPA-smectite, although uptake at relatively high equilibrium
solution benzene concentrations (C.sub.e >100 ppm) is somewhat reduced
compared to TMA-smectite. Surprisingly, these isotherms show that the
ratio of sorbed benzene to benzene remaining in solution is initially very
large, i.e. at C.sub.e <100 to 200 ppm, but decreases as the amount of
sorbed benzene increases. This type of sorptive behavior is characteristic
of surface adsorption, and contrasts to the partition behavior of
HDTMA-smectite where the ratio of sorbed to solution phase aromatic
hydrocarbon remains relatively constant over a wide range of C.sub.e
values.
The sorption isotherms of FIG. 2 also show that TMPA-smectite is a far more
effective adsorbent for alkylbenzenes and naphthalene than TMA-smectite.
The sorptive capability of TMA-smectite decreases markedly as the size of
the alkyl substituent increases in going from benzene to toluene to
ethylbenzene to xylene to butylbenzene. In the case of TMPA-smectite,
however, the high uptake from water is also observed for toluene,
ethylbenzene, xylene, butylbenzene and naphthalene. Thus, while
TMA-smectite exhibits strong shape selectivity and is a poor sorbent for
alkylbenzenes and naphthalene, TMPA-smectite shows no steric exclusion and
effectively removes these compounds from water.
The high affinity of TMPA-smectite for the highly water soluble aromatic
constituents of petroleum is important because these compounds represent
some of the most common organic ground water contaminants. Thus, in
accordance with the present invention, TMPA-smectite and other tri-short
chain alkyl mono-acyclic-smectites have great utility as liner materials
for petroleum containments, as for example in tank farms and underground
storage tanks. The use of tri-short chain (C.sub.1 -C.sub.4), mono-
substituted or unsubstituted cycloalkyl, aryl, or alkaryl
ammonium-smectites:
##STR11##
, wherein R is a substituted or unsubstituted cycloalkyl moiety or a
substituted or unsubstituted cycloalkyl moiety or a substituted or
unsubstituted aryl or alkaryl moiety; and where R' is C.sub.1 -C.sub.4 or
a substituted or unsubstituted cycloalkyl moiety, or a substituted or
unsubstituted aryl or alkaryl moiety, in conjunction with Na-smectite in
such applications results in a liner composite with the desirable
properties of low hydraulic conductivity (derived from Na-smectite), and
high sorptive removal of water-laden hydrocarbon contaminants aromatic
hydrocarbon contaminants (derived from TMPA-smectite).
The effects of layer charge of the clay mineral used to prepare the
TMPA-smectites was evaluated using smectites with a layer charge of 0.64
(denoted SAC) and 0.96 (denoted SWa) mol.sup.- /unit cell (TABLE 2). The
effect of layer charge on the sorptive capabilities of the TMPA-smectites
was dramatic as illustrated in FIG. 3. The low-charge (SAC) TMPA-smectite
was a much more effective adsorbent for removing benzene and toluene from
water than was the high-charge (SWa) TMPA-smectite. Apparently in these
clays, the closer packing of exchanged TMA or TMPA ions in the clay
interlayers results in restricted access of the aromatic molecules to the
interlamellar regions.
Clearly, the effect of layer charge is different for TMPA-smectites than
that observed previously for HDTMA-smectites. The larger quantity of
exchanged HDTMA in higher charge smectites enhances sorption of benzene
and toluene relative to the lower charge analogs. Yet, a greater quantity
of exchanged TMPA in SWa-TMPA results in less benzene uptake than by
SAC-TMPA. These observations are consistent with the different sorptive
mechanisms of the organo-clays, i.e., the partition behavior of
HDTMA-smectite versus the adsorptive behavior of TMPA-smectite.
In accordance with the present invention, replacing the exchangeable
inorganic cations of a low-charge smectite (e.g., SAC) with TMPA cations
results in an organo-clay that can effectively remove hydrocarbon
contaminants, e.g. benzene, alkyl-substituted benzenes and naphthalene
from water. The Langmuir-type adsorption isotherms exhibited by
TMPA-smectite make this organo-clay an especially effective adsorbent at
low (<0.1 to 0.2) relative equilibrium solution concentrations
(equilibrium concentration/water solubility of the solute). In this
concentration range, TMPA-smectite is the most effective organo-clay yet
developed for removing aromatic hydrocarbons from water.
While there have been illustrated and described various embodiments of the
present invention, it will be apparent that various changes and
modifications will occur to those skilled in the art. It is intended in
the appended claims to cover all such changes and modifications as fall
within the true spirit and scope of the present invention. Additionally,
it should be understood that the foregoing description is to be construed
as illustrative and not in any limiting sense.
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